1. Field of the Invention
The present invention relates to semiconductor devices, and particularly to a semiconductor device configured to prevent analysis of the structure of its circuit component portion and to make it difficult copy or altering of information in the circuit.
2. Description of the Background Art
In a semiconductor device, a number of semiconductor elements formed on a substrate with electrode interconnection established are generally protected from influences of ambience such as alpha ray, moisture and stress by covering a circuit component portion with an insulating protection film so as to prevent malfunction due to moisture invasion and the like, change in characteristics caused by stress, and the like. A silicon oxide film, a silicon nitride film and the like are usually employed as the protection film covering the circuit component portion.
There are some circuit component portions of semiconductor devices which have taken a long period of time for development thereof or which are superior in originality. Therefore, they should preferably be protected from imitation and copy thereof by other people. Further, there is some memory device storing important information in the circuit of the semiconductor device, and thus the information should preferably be protected from being altered.
However, the insulating protection film mentioned above is provided for protecting the circuit component portion from ambience. Therefore, the film is usually superior in optical transmissivity relative to visible light and far-infrared radiation, so that the circuit component can easily be discerned from above the protection film by a visible light microscope or an IR (infrared) microscope, leading to a high possibility of imitation and copy of the circuit component portion or altering of the information in the memory device.
The present invention is made to solve those problems described above. One object of the invention is to provide a semiconductor device having a circuit component portion which is difficult to analyze so as to prevent copy, imitation and altering of information by other people.
According to one aspect of the present invention, a semiconductor device includes a substrate having a circuit component portion, an insulating protection film formed to cover the circuit component portion, an analysis prevention film formed on the protection film to cover a main part of the circuit component portion for preventing analysis of the main part, and a corrosion resistant film formed to cover the analysis prevention film for preventing the analysis prevention film from being ruined by a chemical solution.
Employment of the structure above, which has the analysis prevention film covering the main part, can make it impossible to analyze an underlying circuit pattern.
According to another aspect of the present invention, a semiconductor device includes a substrate having a circuit component portion, an insulating protection film formed to cover the circuit component portion, and an analysis prevention film formed on the protection film to cover a main part of the circuit component portion for preventing analysis of the main part, the analysis prevention film having corrosion resistance for preventing itself from being ruined by a chemical solution.
Employment of the above structure can deter an attempt to achieve analysis by performing chemical solution processing on the analysis prevention film for removing the film, since it is difficult to destroy the analysis prevention film by a chemical solution even if a corrosion resistant film is not separately provided.
Preferably, the semiconductor device according to the invention further includes an interconnection which is placed between the substrate and the protection film to reach the circuit component portion. The protection film has an opening located in a region which is not covered with the analysis prevention film to reach the interconnection. Employment of this structure can deter an attempt to remove the analysis prevention film by the chemical solution processing and thus analyze the circuit pattern, since the chemical solution entering through the opening first removes the interconnection and the circuit component portion.
Preferably, in the semiconductor device according to the invention, the analysis prevention film and the protection film have their surfaces substantially at the same height. Further, the surface of the protection film is preferably flat. Employment of this structure can prevent an attempt to recognize the entire shape of underlying interconnections and positional relation thereof based on roughness of the surface.
Preferably, in the semiconductor device according to the present invention, the analysis prevention film is formed of the same material as that of the interconnection. In this structure, if chemical solution processing is performed on the analysis prevention film to eliminate the prevention film, the interconnection could also be eliminated under the same condition and consequently the interconnection disappears before being analyzed. In this way, the analysis can be prevented.
According to the present invention, preferably the analysis prevention film is formed of an electrically conductive metallic film. Employment of this structure in which the analysis prevention film has a low transmissivity relative to visible light and IR radiation can prevent analysis of an underlying circuit pattern.
According to the one aspect of the invention, preferably the electrically conductive metallic film is formed of an electrically conductive metal material. By employing this structure, an analysis prevention film having a low transmissivity relative to visible light and IR radiation can easily be accomplished.
According to the one aspect of the invention, preferably the electrically conductive metallic film is a metallic film formed of at least one of titanium nitride and titanium-tungsten alloy. Even if the analysis prevention film is not formed of a metal material, employment of the structure above can achieve an analysis prevention film having a low transmissivity relative to visible light and IR radiation.
According to the one aspect of the invention, the corrosion resistant film is preferably formed of aluminum oxide. Employment of this structure can protect the analysis prevention film from a chemical solution since the aluminum oxide has a superior corrosion resisting effect.
According to the one aspect of the invention, preferably the corrosion resistant film is formed of dyed aluminum oxide. It is possible to make it further difficult to visibly discern an underlying circuit pattern by employing this structure.
According to the another aspect of the invention above, preferably the analysis prevention film is formed of an electrically conductive metallic film having corrosion resistance. Further, according to the another aspect of the invention, preferably the electrically conductive metallic film is a metal film formed of at least one of tantalum and niobium. Employment of this structure can accomplish an analysis prevention film having corrosion resistance.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.